This invention is concerned with a gage for measuring the center height of a cylindrical workpiece to be cut by a cut-off tool.
Cut-off tools are used to cut off the end part or end parts of pieces subjected to metal cutting operations. Such ends are usually cylindrical and it is important that the tool be set with respect to the center height of the workpiece end at a certain amount to ensure proper cutting action, e.g. about 0.007 in. above centerline. If the cut-off tool is too far above the centerline the tool will push the part off rather than cut it. If the tool is below centerline it passes beneath the center of the part and breaks it off or the tool itself will break.
The most common method of setting the cut-off tool to center height on a screw machine is by using a solid test bar. In this procedure the cut-off tool holder and blade assembly are mounted onto the cross-slide so that the cutting edge of the blade will cut slightly above the center of the test bar and the leading edge of the blade will reach the center of the test bar when the cross-slide is at high point. The test bar is positioned so the cut-off tool will only make a narrow cut, approximately 1/16 in. in the bar. This cut will leave a small nib at the center of the test bar. The diameter of the nib is then measured with calipers or a micrometer. One half of this measurement is taken and the cut-off tool holder and blade assembly is raised on the cross-slide that distance. A second test cut is then made. If a clean cut is made without leaving a nib or galled surface at the center of the test bar, the cut-off tool is on center.
Another common method is to take several trial cuts and closely observe the tool as it goes to center.
The above described method of centering cut-off tools are time consuming and inaccurate for the most part.
If the height from the cut off tool's cutting point to the centerline of the bar can be predetermined the tool can be readily adjusted. One way to accomplish this is by use of a gage which will determine center height of the cut-off tool relative to the centerline of the piece.
One centering gage currently available contains magnetic locaters which are placed against the end piece to be cut and is equipped with a bubble site level. By adjusting the cutting tool so that the tip is in contract with the levelled gage the work centerline is determined. This gage is used primarily for turning tools and has the disadvantage of assuming the side of the gage is parallel to the floor and that the machine holding the piece is level. In many cases the slide of the cut-off tool is also not level.
The present invention, on the other hand, provides a center height gage for a cut-off tool which provides an accurate and speedy determination of the deviation above or below centerline of the cut-off tool which accuracy extends over a wide range of diameters of end pieces to be cut thereby having wide application in metal cutting operations.